The present invention relates generally to devices used to control the flow of petroleum fuel vapors between a carbon canister and a combustion engine.
In order to comply with state and federal environmental regulations, most motor vehicles are now equipped with a carbon canister installed to trap and store petroleum fuel vapors from the carburetor bowl and/or the fuel tank. With the canister, fuel vapors are not vented to the atmosphere, but are instead trapped in the canister and then periodically purged from the canister into the engine where they are burned along with the air-fuel mixture. A solenoid valve is typically used to control purging of the carbon canister.
It happens that the carbon canister solenoid valves can be adversely affected by airborne carbon particles traveling through the system with the petroleum fumes. More specifically, carbon particles can block full closure of the valves and cause leakage and test fail on the xe2x80x9cOn Board Diagnosticxe2x80x9d (OBD) within the motor vehicle.
The common way to solve the carbon contamination problem is to install a filter at the inlet of the solenoid valve, e.g., an eight-tenths millimeter (0.8 mm) mesh filter to trap the larger carbon particles. Unfortunately, as understood herein, these filters need to be cleaned or replaced many times during the life of the solenoid valve to avoid blocking the flow of air through the valve. Moreover, the present invention recognizes that an eight-tenths millimeter mesh filter will not collect smaller particles that can also cause leakage and diagnostic failure.
In light of the above problems, the present invention recognizes a need for a device for controlling the purging of a carbon canister that will minimize contamination by larger carbon particles.
A solenoid valve for a vehicle carbon canister includes a housing that has an outlet port, a cylindrical housing wall and an inlet port. Within the housing is a solenoid mechanism that establishes an annular air passage between the solenoid mechanism and the housing wall. The solenoid valve also includes an air inlet tube that extends away from the inlet port of the housing and communicates with the annular air passage. Furthermore, an outlet nipple that has an internal portion extends inwardly from the outlet port, such that it establishes an annular cavity between the internal portion of the outlet nipple and the housing. This annular air cavity communicates with the annular air passage and as petroleum fumes pass through the valve the annular air cavity traps carbon particles. The solenoid mechanism has a plunger within that moves to selectively block the flow of air through the air outlet nipple.
As envisioned in the particularly preferred embodiment set forth below, the annular air passage has a thickness between five hundred and eight hundred microns. Moreover, the solenoid valve has an inlet end that forms the inlet port and at least one hole that has an electrode disposed therein. The electrode connects to the solenoid mechanism and provides power to the coil. Finally, in the preferred embodiment, the housing extends outwardly around the hole in the inlet end and forms a female socket.
In another aspect, the solenoid valve for a vehicle carbon canister includes a hollow housing that has an outlet end, a cylindrical housing wall, and an inlet end that forms an inlet port. Within the hollow housing is a cylindrical solenoid mechanism. An end cap that forms an outlet port is also disposed in the outlet end of the housing. The addition of the solenoid mechanism within the solenoid valve of the present invention forms an annular air passage between the solenoid mechanism and the hollow housing.
The end cap forms an air outlet nipple that has an internal portion and an external portion that extends inwardly and outwardly around the outlet port. With this structure, the air outlet nipple forms an annular cavity between the internal portion of the air outlet nipple and the hollow housing. Fluid communication between the air inlet tube, the annular air passage, and the air outlet nipple forms a continuous air passage and as petroleum fumes pass through the valve, the annular cavity receives carbon particles that are present in the fumes. Finally, this aspect of the present invention includes a valve that selectively blocks the flow of air through the continuous air passage.
In still another aspect, a solenoid valve for a vehicle carbon canister includes a housing that forms an inlet port and an outlet port. Also, the housing includes a continuous side wall. A solenoid mechanism is in the housing, and an annular air passage is established between the solenoid mechanism and the housing wall. The air passage has a width of between five hundred microns and eight hundred microns, and the passage communicates with the ports in the housing.
As set forth in greater detail below, this aspect of the solenoid mechanism includes a plunger that is movable between an open position, wherein the outlet port is not blocked and purge air communicates with the carbon canister, and a closed position, wherein the outlet port is blocked. An outlet nipple is juxtaposed with the outlet port, and the nipple includes an internal portion that is at least partially surrounded by the housing wall such that a cavity is established between the internal portion of the nipple and the housing wall. With this structure, at least some particles in air that flows from the inlet port to the outlet port through the annular air passage are held in the particle-holding cavity.